Transfer Speed is very slow, ODROID XU-4

Hey mates,
my computer and the odroid have gigabit LAN and i already checked this. The speed on the Odroid is listed at 1000Mb/s (ethtool). A WD RE4 Harddrive is connected to the odroid with a Seagate Case. FTP and SMB are set up, but when i want to transfer my files, the speed is only about 10 to 12mb/s. Something must be wrong there, but i don't know what. Can somebody may help me? ;D

I tried something and found this out: If i flash it again. I got around 70MB/s which is fine for me. But when i change the power management of the harddisk(Spindown after 20 min and APM -1) then the speed slows down to 12,5MB/s. Even if i roll back these options the speed stays that low. This doesn't seems very logical for me...